1. Field of the Invention
This invention relates to control devices, and particularly to an alternating current sensor and control device which senses the presence of an alternating current load in a circuit, signals the fact that the alternating current circuit is energized, and which disables the alternating current circuit if the sensing and signaling means are disabled or inoperative.
2. Description of the Prior Art
U.S. Pat. No. 3,258,693 discloses a device for indicating an abnormal flow of current in a utilization circuit. The utilization circuit includes a glow discharge device. When normal current is flowing through the utilization circuit, the current load is not sufficient to illuminate the glow discharge device. However, if an abnormal amount of current flows through the utilization circuit, then the glow discharge device is illuminated and indicates the abnormal condition.
U.S. Pat. No. 3,768,012 teaches a power supply direct current detector system for direct current power supplies in which the direct current power supply uses a filter choke inductor. The detector uses the winding resistance of the filter choke to sense the direct current output. Two problems are explained with respect to this method of detecting current. One problem is the fact that the voltage developed across the inductance of the choke must be rejected. The second problem is that the temperature drift of the choke winding resistance must be compensated. According to the specification of this patent, both of these problems are solved by the direct current detector system taught by this patent.
U.S. Pat. No. 3,857,096 relates to an electrical current leakage detector circuit in which an induction coil is used to detect the flow of current in a conductor, with a differential amplifier connected to the secondary coil to detect the flow of extremely small currents. The differential amplifier is in turn connected to a visual or audible device for indicating the presence of electrical current in the circuit.
U.S. Pat. No. 3,863,150 discloses a structure which may be constructed in the form of a male-female plug that indicates first whether or not the circuit into which the plug is connected is an active circuit, and secondly, whether the implement connected to the plug is drawing current from the circuit.
U.S. Pat. No. 4,052,664 illustrates still another device for monitoring an electrical circuit to determine whether the power is on and the circuit is working.
The prior art is of course replete with sensing and indicating devices that can be tapped into both alternating and direct current circuits to signal the fact that a circuit is energized. While all of these sensing and signaling devices are important and serve a useful function, it is surprising that the patent literature does not teach, nor is there available on the market, a sensing and signaling device that incorporates a safety function that disables the alternating current circuit if the sensing and signaling device is either omitted or is itself disabled for any reason.
Accordingly, it is one of the important objects of the present invention to provide a current sensing and circuit control device that incorporates a sensing and load signaling means which disables the alternating current circuit to which it is connected if the sensing and load signaling means is removed from the circuit or is disabled for any reason.
Another object of the invention is to provide a current sensor and circuit control device which senses the presence or absence of alternating current in a circuit and signals the fact that alternating current is being drawn from such circuit.
Still another object of the invention is the provision of an AC current sensor and control device incorporating a sensing and circuit load means effective to control one or more alternating current outlets in the circuit.
There are many circuits that are equipped with sensing and signaling devices to indicate that a circuit is energized, i.e. that voltage and current are present in the circuit. However, I have been unable to find any such safety devices incorporated in alternating electrical circuits in which energization of the entire AC distribution circuit is dependent on the sensor and circuit load means drawing current from the circuit. Accordingly, a still further object of the invention is the provision of a current sensing and control device for use with a power distribution device such as a power strip including a multiplicity of AC power outlet receptacles, in which one of the receptacles accommodates a current sensing and circuit load device the operation of which controls the transmission of electrical current to all the other outlet receptacles in the power strip.
Another object of the invention is the provision of a junction box in the nature of a receptacle having a plurality of outlet receptacles all of which may be connected to a source of AC electrical energy, and all of which electrical outlet receptacles are controlled in the performance of their intended function of power distribution by the performance of sensing and circuit load means operatively connected into the circuit.
Still another object of the invention is the provision of a current sensor and circuit control device incorporated into a power distribution device in which a multiplicity of electrical outlet receptacles are controlled by operation of a sensing and signaling means which indicate that a load is being imposed on the circuit, and which has a very wide range of operation, sensing a load as low as 3 watts and as high as several thousand watts without any modification or "pre-programming" of component values for a particular range of operations.
Still another object of the invention is a current sensor and control device which can be built into a small enclosure, e.g., a conventional power distribution strip, a stand-alone box or a wall receptacle.
A still further object of the current sensor and control device is to provide a circuit switching capability incorporating a safety feature which has wide application in the switching field, e.g., in a situation where multiple switched outlets and one sense and control outlet is provided, this invention can be used to activate other associated devices when the sense and control outlet is energized. In like manner, in an application, e.g., involving a component stereo system, this invention can be used to activate simultaneously the receiver, tape deck, and pre-amp and other components associated with the stereo system when the sense and control receptacle is energized. With the advent of computers, and word processing equipment controlled by computers, there are many components that must individually be turned on when the computer is turned on. This is not always convenient. The power switches for the separate components are not always easy to reach; the sequence in which they are turned on is not always advantageous; and if one essential component is not turned on through inadvertence, it can disrupt the operation of the entire computer system. Accordingly, it is another object of the present invention to provide a current sensing and control device which may be utilized in this environment whereby energizing the sense and control load will effectively simultaneously activate the disc drive, the line printer, the terminal, the video monitor, and any other selected components.
There are other applications in which it is advantageous that an electrical power outlet strip for electrical power distribution and having multiple electrical outlets be provided with multiple sense outlets and only one switched or controlled outlet. In this application, the current sensor and control device of the invention may be incorporated so that the switched or controlled outlet is activated if any of the sensed outlets are activated. Accordingly, it is another object of the present invention to provide a current sensor and control device that will fulfill this function.
The invention possesses other objects and features of advantage, some of which, with the foregoing will be apparent from the following description and the drawings. It is to be understood that the invention is not limited to the embodiment illustrated and described, since it may be embodied in various forms within the scope of the appended claims.